In the ammonia developing process an excess of ammonium hydroxide is introduced into the developer system to provide a hot, moist alkaline environment. In a conventional ammonia type diazo machine the residue waste of aqueous ammonia solution is drained from the developer system to a waste collection container and the container is periodically emptied. To eliminate this inconvenient and undesirable procedure, and to avoid escape of ammonia gas or fumes to the atmosphere, the present invention provides a convenient and safe arrangement for eliminating the residue waste without the need of emptying the waste container and without requiring intervention by the machine operator in any way.